Synthesis of spherical zirconia by reverse emulsion precipitation

Spherical ZrO₂ microparticles were prepared in a three-phase reactor by mixing two water-in-oil emulsions with normal heptane as oil phase and aqueous solutions of zirconium oxyacetate and ammonia as water phases, respectively. The principal factors that influenced the stability of emulsion were investigated, including the surfactant type, the volume of w/o, and the concentration of zirconium ion. In this work, four anion surfactants were tested, including Span 85, Arlacel 83, Span 80 and Span 40. The most stable reverse emulsions were obtained with the surfactant Span 40. When w/o volume ratio was kept 1/100 using Span 40 or Span 80 as a surfactant, the ZrO₂ microparticles with spherical morphology were successfully prepared in the reverse emulsions at various Zr⁴⁺ concentrations (from 0.5 M to 3 M). The particle sizes of ZrO₂ are smaller for Span 40 as compared with Span 80 on the same Zr⁴⁺ concentrations. The crystalline phase of the ZrO₂ powders after calcination at 750 °C for 2 h was tetragonal.     

Oil and water determination in emulsions by pulsed low-resolution NMR

A pulsed, low-resolution nuclear magnetic resonance (NMR) technique has been used for the oil and water determination in O/W emulsions. The method is based on the analysis of the longitudinal magnetization decay curve, that, due to the different relaxation times of oil and water, consists of 2 recognizable components. Correlation of NMR results with fat content is described. A good correlation between the NMR response and fat content by weight has been found. The rapidity and accuracy of the measurements are comparable to those of other techniques.     

环己烷/水乳状液的超声破乳

为排除污油等复杂乳化液中的杂质干扰,采用单一组分方法,制备不同体系的环己烷/水乳状液,研究超声在乳状液中的破乳作用,考察超声声强、超声频率、超声辐照时间对乳状液破乳的影响。结果表明:乳状液的初始水含量对超声破乳效果有影响,初始水含量越低,破乳效果越好;超声声强的改变直接影响乳状液分散相液滴的凝聚和发散,超声破乳的声强应在空化临界阈值以下,以0.66 W/cm2最佳;超声辐照时间为6 min,超声频率为20 kHz时破乳效果达到最好。     

球形氧化锆的湿法制备过程研究

以氯氧化锆和碳酸氢铵为原料，采用连续反应沉淀法制备了微米级球形氧化锆前驱体，此前驱体在500℃下于空气气氛中煅烧2h得到球形氧化锆粉体。探讨了锆盐溶液浓度、加料速度、pH、反应时间对粉体颗粒粒径大小及其分布的影响。经SEN，XRD，TG—DSC和激光粒度测试仪分析，结果表明在最佳工艺条件下制备的氧化锆前驱体颗粒呈球形，分散性好，粒径分布在8—18μm。     

Uniform precipitation of Yttria-Stabilized zirconia

An experiment on precipitation of zirconia by urea, urotropin, and ammonium hydroxide precipitants is described. The morphological and phase composition of the precipitated powders are investigated. It is shown that a buffer has a positive effect on reducing the agglomeration. The agglomeration factor for the ammonium hydroxide precipitant is reduced from 175 to 40. A powder consisting of soft agglomerates having a developed surface and easily disintegrated in milling to a size of < 1 µm is obtained. Individual particles are 0.06–0.08 µm in size.Translated from Ogneupory, No. 6, pp. 2–5, June, 1995.The work has been supported by the Fund for Fundamental Investigations of the Russian Academy of Sciences.     

Synthesis of zirconia toughened alumina nanopowders as soft spherical granules by combining co-precipitation with spray drying

The nanopowders of zirconia toughened alumina (ZTA) as soft spherical granules were directly synthesized by combining co-precipitation with spray drying (CPSD). The co-precipitation of alumina (Al₂O₃) and yttria-stabilized zirconia (YSZ) was performed together in one step to obtain the ZTA precipitate. Spray drying, which is the most preferred industrial processing way to produce the nanopowders as spherical granules, was used to atomize, dry and granulate the suspension like milk prepared from the synthesized ZTA precipitate under previously optimized spray drying conditions. However, the important and complex processing parameters of spray drying such as the solid-liquid ratio and the feeding rate of the suspension, the inlet temperature and the flow rate of the hot air have to be optimized depending on the moll mass and volume of the component in the prepared suspension. The ZTA nanopowders containing 4–20 wt% YSZ synthesized by the CPSD method have a crystalline structure of alumina and YSZ, an average nanoparticle size between 26.64 and 46.70 nm with a very high specific surface area (SSA) between 77.43 and 112.41 m² g⁻¹ in a soft spherical granule form, which were determined by XRD, BET and SEM, respectively. The preparation and drying conditions of the synthesized precipitate, the solid-liquid ratio of the suspension and the molar mass ratio of YSZ in Al₂O₃ matrix have a significant effect on the crystallinity, morphology, particle size, SSA, and granule form of the synthesized ZTA nanopowders.     

Safety investigations of trinitrotoluene/water emulsions

In the disposal of explosives, preparation of the dismantled material is necessary before subjecting it to a breakdown process. Knowledge of the material properties and determination of safety-related parameters are major prerequirements when designing a disposal facility and increasing handling safety. When TNT is treated using emulsion processing, a desensitization of the TNT melt via the aqueous phase is obtained, in addition to increasing the surface area of the TNT phase. During the entire process of TNT treatment, the system is exposed to a wide range of different stresses as a result of the mechanical energy applied. This study presents the results of an investigation on the sensitivity of pure TNT melts and TNT/water emulsions at different concentrations on exposure to the applied impact or shock energies. It is found that the impact sensitivity of a TNT/water emulsion is lower by a factor of 4 when the TNT concentration has been reduced from 50 wt % to 30 wt %. On exposure to stress from a detonation shock wave, a desensitization of the system due to the aqueous phase is also found, so that the safety of the TNT treatment process can be increased by using a TNT/water emulsion when applying mechanical breakdown methods.     

沉淀法制备铈掺杂氧化锆陶瓷粉体材料的研究

采用化学沉淀法以ZrOCl2.8H2O和Ce2(CO3).8H2O为反应物,制得铈掺杂氧化锆陶瓷粉体材料,研究了反应温度、氧化铈的摩尔含量、pH、沉淀剂对铈掺杂氧化锆陶瓷粉体的影响。通过XRD谱图表明未掺杂的产品为单斜相,掺杂的产品为单斜与四方相共存,表明在室温下掺杂了的氧化锆可以以亚稳的四方相存在。     

Oil recovery from oil in water emulsions using a flotation column

A flotation column was used to recover oil from oil in water emulsions. The feed oil concentrations investigated were relatively high, in the range of 0.25 to 8 percent by volume. Previous studies using conventional flotation cells dealt with very dilute systems where the oil concentration was less than 0.1 percent by volume. The oil recovery was found to decrease with an increase in the feed oil concentration. The addition of wash water to the froth zone of the column had little effect on the oil recovery. The oil recovery decreased with increasing feed flow rate and surfactant concentration. The effect of increasing the gas flow rate was to initially increase the oil recovery. The oil recovery data were analyzed using a kinetic model. The order of the flotation kinetics was found to be 0.6. The gas hold-up behaviour of the recovery and the froth zones of the flotation column is found to correlate well with the drift-flux model.     

Oil removal from crude oil-in-saline water emulsions using chitosan as biosorbent

ABSTRACT

The sorption of oil from crude oil-in-saline water emulsions was studied using chitosan as biosorbent. The main parameters investigated were chitosan dosage, contact time, and initial crude oil concentration at fixed initial pH. The results showed that the sorption equilibrium was reached within 120 min at oil content as low as 20 mg L^?1. Sorption depends on initial oil concentration and sorbent dosage and may reach up to 95% efficiency in the most favorable conditions. The residual oil concentrations obtained after sorption were always beneath the official limit of oil discharge into environment.     

Effect of spherical porosity on co-fired dense/porous zirconia bi-layers cambering

Geometrical instability leading to cambering is recorded during co-sintering of zirconia dense/porous bi-layered planar structures. Sintering strain in the bi-layers rises mainly from mismatch between the different porosity volume fractions at the layers and their interface. In this paper, we analyze the model case of dense taped of 8 mol% Y₂O₃-stabilized ZrO₂ laminated on ca. 400 μ thick 3 mol% Y₂O₃ doped zirconia porous tapes, with homogenous spherical porosity of 13 vol%, 46 vol%, and 54 vol%. Sintering stress during densification is evaluated from the shrinkage rates and viscoelastic behavior during sintering by thermo-mechanical analysis, using cyclic loading dilatometry. The camber development of the bi-layers is measured by in-situ optical dilatometry. In accordance with the model prediction, cambering can be controlled tuning the porosity while achieving a synergetic effect between densification and formation of open porosity at the bilayers.     

交联型聚硅氧烷/聚丙烯酸酯复合乳液的制备

在甲基丙烯酰氧丙基三甲氧基硅烷存在下，以交联的聚硅氧烷为种子，丙烯酸酯单体为第二单体，偶氮二异丁腈为引发剂，分别采用间歇法、溶胀法和半连续法制备了聚硅氧烷／聚丙烯酸酯复合乳液。采用透射电子显微镜对乳胶粒子形态进行了表征，发现乳液中形成了以聚丙烯酸酯为核、聚硅氧烷为壳的反相核壳结构乳胶粒子；放置90天后，乳胶粒子的形态未发生翻转；将复合乳液破乳后分析，聚合物凝胶量达到96％以上，说明聚合体系交联很好。     

溶液燃烧法制备纳米ZrO_2

实验对比了以甘氨酸和CH6N4O作为燃烧反应的还原剂,与硝酸氧锆配制成氧化-还原性水溶液,在微波炉内加热升温,经历一个约2 m in的快速燃烧后,得到二氧化锆产物。结果表明,用CH6N4O能得到纯度高、粒度分布窄、细小的二氧化锆。通过X衍射法测定,平均粒径为53 nm。     

Enhanced oil recovery using nanoparticle-stabilized oil/water emulsions

We experimentally investigated nanoparticle-stabilized emulsions for enhanced oil recovery (EOR) applications. The emulsions were injected into a silica bead column containing mineral oil, and the oil recovery was calculated using a mass-balance approach. The experiments were carried out as follows: 1) The emulsions were injected into a column with 100% water saturation to investigate the mobility of the water and emulsions, 2) Water flooding was then carried out at initial oil and water saturation, and the emulsion flooding was injected to calculate the enhancement in the oil recovery rate. The results indicate that the nanoparticle-stabilized emulsions increased the oil recovery rate by 11% after water flooding. The mechanism for this is attributed to a greater pressure difference across the porous medium, leading to oil remaining in the pores being produced via a piston effect. These results indicate that nanoparticle-stabilized emulsions may be effective EOR agents.     

Crystallization of glycine in water/saturated fatty acid emulsions

It was found that carbon chain length of fatty acids strongly affects polymorphic selection in the cooling crystallization of glycine from water/saturated fatty acid emulsions. Two-dimensional packing density of saturated fatty acid head groups, which is inversely proportional to the number of carbon atoms, was shown to be responsible for polymorphic selection of glycine: γ-glycine was obtained from the emulsions of hexanoic acid and octanoic acid, whereas α-glycine was found to crystallize from the emulsions of dodecanoic acid, tetradecanoic acid, hexadecanoic acid and octadecanoic acid. Those results indicate that molecular structure of γ-glycine is only well matched with molecular structure of head groups of hexanoic acid and octanoic acid at the interface of the emulsion, and thus such molecular interface provides the preferential site for the organization of γ-form crystal structure from the liquid-like cluster of glycine.     

Synthesis of highly selective spherical caffeine imprinted polymers via ultrasound‐assisted precipitation polymerization

A facile and efficient method for synthesis of molecularly imprinted polymers via ultrasound‐assisted precipitation polymerization was developed. Caffeine was applied as a model template in the imprinting using methacrylic acid and ethylene glycol dimethacrylate as a functional monomer and a crosslinker, respectively. Polymerization under sonochemical conditions proceeded rapidly (within 3 h at 60°C) to afford polymer microspheres with narrow size distributions in excellent yields while maintaining the binding specificity toward the template. It was found that the imprinted polymer prepared at low initial temperature (40°C) exhibited the best caffeine binding performance in terms of specificity and selectivity. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

对油水乳浊液分离的研究

本文主要研究了操作条件的改变对分离效果的影响，在研究中还考察了NaCl和絮凝剂加入乳浊液后对分离过程产生的增效作用。得到了一个与实验数据相关联的数学方程，为估算油的去除率提供了一个有用的工具。在电浮选装置中采用不溶电极，为今后的分离技术提供了一个新思路。     

液相沉淀法制备单分散亚微米级球形碳酸锰

以硫酸锰为锰源,碳酸氢铵为沉淀剂,十二烷基硫酸钠为粒径控制剂,采用硫酸锰和碳酸氢铵两种溶液快速同时加入的方式,通过控制合适的反应结晶条件,制备出亚微米级单分散球形碳酸锰颗粒.借助扫描电镜(SEM)、X射线衍射(XRD)、粒度分析仪等研究了反应结晶条件对碳酸锰粒径和形貌的影响.结果表明,在硫酸锰浓度为1.2 mol/L、碳酸氢铵浓度为0.7 mol/L、反应温度为30 ℃、反应时间为30 min、碳酸氢铵与硫酸锰物质的量比为1.5:1的条件下,可以得到平均粒径约为540 nm的单分散球形碳酸锰微粒.